Float problem

[MarcinKlima]

Hi im got a problem with float on python side (RX), got a this kind of output: b'P'2.1579996350602183e-43
When im sending from uC:
testStruct.z = 'P';
testStruct.y = 4.55;
Betwen uC is no problem work like a harm, on python floats crazy.
9600 baud / Python 3.9.2 / Debian

[PowerBroker2]

Without looking at your code, you're most likely not using 32 bit floats on the Arduino side. If you replace float with double, you should be good to go.

[MarcinKlima]

Yes, my mistake, is fact.
But when im try examples from GIT, nothing working, only CHAR variable has expected value, in y have 0.0, arr has "nothing".

Raw example generate like this:
unpacked_response = unpacked_response.decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xeb in position 3: invalid continuation byte

---

Arduino:

#include <Arduino.h>
#include <Wire.h>
#include <SerialTransfer.h>

HardwareSerial Serial2(PA3,PA2);

SerialTransfer myTransfer;

struct STRUCT {
char z;
double y;
} testStruct;

char arr[] = "hello";

void setup() {
Serial2.begin(9600);
myTransfer.begin(Serial2);

analogWriteResolution(12);

pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, HIGH);

testStruct.z = '$';
testStruct.y = 5.25;

}

void loop() {

// use this variable to keep track of how many
// bytes we're stuffing in the transmit buffer
uint16_t sendSize = 0;

///////////////////////////////////////// Stuff buffer with struct
sendSize = myTransfer.txObj(testStruct, sendSize);

///////////////////////////////////////// Stuff buffer with array
sendSize = myTransfer.txObj(arr, sendSize);

///////////////////////////////////////// Send buffer
myTransfer.sendData(sendSize);

testStruct.y = testStruct.y + 0.1;

digitalWrite(LED_BUILTIN, LOW);
delay(100);
digitalWrite(LED_BUILTIN, HIGH);
delay(100);

}

Python:

from time import sleep
from pySerialTransfer import pySerialTransfer as txfer

class struct(object):
z = ''
y = 0.0

arr = ''

if name == 'main':
try:
testStruct = struct
link = txfer.SerialTransfer('/dev/ttyUSB0', baud=9600)

    link.open()
    sleep(5)

    while True:
        if link.available():
            recSize = 0
            
            testStruct.z = link.rx_obj(obj_type='c', start_pos=recSize)
            recSize += txfer.STRUCT_FORMAT_LENGTHS['c']
            
            testStruct.y = link.rx_obj(obj_type='f', start_pos=recSize)
            recSize += txfer.STRUCT_FORMAT_LENGTHS['f']
            
            arr = link.rx_obj(obj_type=str,
                              start_pos=recSize,
                              obj_byte_size=6)
            recSize += len(arr)
            
            print('{}{} | {}'.format(testStruct.z, testStruct.y, arr))
            
        elif link.status < 0:
            if link.status == txfer.CRC_ERROR:
                print('ERROR: CRC_ERROR')
            elif link.status == txfer.PAYLOAD_ERROR:
                print('ERROR: PAYLOAD_ERROR')
            elif link.status == txfer.STOP_BYTE_ERROR:
                print('ERROR: STOP_BYTE_ERROR')
            else:
                print('ERROR: {}'.format(link.status))
            
    
except KeyboardInterrupt:
    link.close()

[PowerBroker2]

I've fixed the examples and will tag out a new version soon.

[MarcinKlima]

Ok, find where is problem, im don`t know is the platform STM32/ARDUINO or python issue - but difference bet wen sides is
arduino - recsize is 12... on python showing 8. when im add(4) to be 12 on python, everything work ok. Why?

[PowerBroker2]

The issue isn't on either side, it's how you use the libraries. Python's normal float size is 32 bits and Arduino's normal float size is 16 bits. If you use doubles on the Arduino side, or 16 bit floats on the Python side, you'll be good to go

[MarcinKlima]

Yes im lost 2 days :) for that, mega good library for me.
And numpy and its data types save my life :)
y = np.float16(0.0) etc.
Thank U for support.